An interfacial heat transfer in a countercurrent gas-liquid flow in a trickle bed reactor

The paper is devoted to interfacial heat exchange between gas and liquid flowing countercurrently through a packed bed in a trickling flow regime. The lack of correlations describing the interfacial gas liquid heat transfer coefficient makes problems when numerical models of non-isothermal flows in porous media are being developed. Thus the experimental investigation was undertaken with the use of a column of 0.1 m inner diameter, equipped with 6 mm glass Raschig rings. Air and water were used as working fluids. The loads of media ranged between 0.0177-0.1415 m(3).(m(2) s)(-1) and 0.0007-0.0053 m(3) .(m(2) s)(-1) for gas and liquid phases, respectively. The inlet water temperature was changed within the range between 30 degrees C and 70 degrees C whereas the inlet air temperature was kept constant at the level of (21 +/- 1) degrees C. It was found that interfacial heat transfer coefficient is strongly dependent on the gas load, noticeably dependent on the temperature difference between phases and slightly dependent on the liquid load. The results of the experiment were used to develop a new correlation describing the interfacial heat transfer in the packed bed expressed by the Nusselt number. Various group numbers were considered in order to account for the impact of gravity, surface tension, thermal diffusion and free convection on the interfacial heat transfer. After detailed regression analysis the correlation of the form Nu = Re-G(1.169) . Ga-G(-0.8399) . Eo(0.7176) was finally proposed as the most fitting the experimental data. (C) 2016 Elsevier Ltd. All rights reserved.